Fig. 1.

Morphology of the DMVs induced by SARS-CoV-2 (Wuhan strain) in Vero E6 cells (a) and cultured primary respiratory epithelium (b). The areas outlined by the white squares in a and b are shown at higher magnification in the lower panels. In both cases, the double membrane delineating the interior of the vesicle is visible. However, these two concentric membranes are separated by a wider space in Vero cells than in primary cultures of respiratory epithelium. The wider spacing of the two membranes in Vero cells makes it possible to identify the points of contact between the two membranes (large arrows on the high magnification images shown in the lower panels of a), probably corresponding to pores crossing the two membranes and allowing exchanges with the cytoplasm. These ultrastructural differences cannot be attributed to technical artifacts, as these two cell preparations were fixed and prepared for EM with the same protocol (described in detail in [13]). The small white arrows in a and b indicate the presence of virus particles, formed in the ERGIC compartment (intermediate between the ER and the Golgi apparatus). Some viruses secreted at the apical pole of the primary respiratory epithelium cells are also identified by small black arrows in b. m mitochondria; er endoplasmic reticulum; n nucleus